Additional media processing by gateways

Gateways are often taken as simple convertors between different media formats. Additional application servers are use to provide additional media processing capabilities. But use of additional application server is not always the best solution. In case changes to media should be applied as fast as possible (if possible no delay between user input and initiated by this input action), small and provided to all users (no accounting, billing) set of media control commands it may be better to ingegrate appropriate services in the gateway.

The best suited for this purpose media processing services are:

• Manual gain control by user
• Automatic gain control with possibility of activation/deactivation by user
• Suppression of ambient noises with possibility of activation/deactivation by user
• Mute/Un mute
• Send information tone to peer
  

The mentioned functionality provides the best results if used togewer (on the same media processing resource) with media converion (transcoding) process.

Using Diva hardware and chan_capi it is possible to implement all mentioned above functionality using chan_capi "vc" command and the provided by Diva hardware media processing commands (please read README.media for details).

Here is small example:

[macro-vcmenu]
exten => s,1,capicommand(vc|inctxdgain|1|1.5) ; 1 - increase volume
exten => s,n,capicommand(vc|inctxdgain|2|-2.5) ; 2 - decrease volume
exten => s,n,capicommand(vc|txdgain|0|-128) ; 0 - Mute Tx
exten => s,n,capicommand(vc|txdgain|9|0) ; 9 - Un-mute Tx
exten => s,n,capicommand(vc|soisesuppressor|3|yes) ; 3 - Suppression of ambient noises ON
exten => s,n,capicommand(vc|soisesuppressor|4|yes) ; 4 - Suppression of ambient noises OFF
exten => s,n,capicommand(vc|sendtone|5|0x83) ; 5 - Send tone
exten => s,n,capicommand(vc|stoptone|6|) ; 7 - Stop tone
exten => s,n,capicommand(rxagc|yes) ; Activate Rx AGC
exten => s,n,capicommand(txagc|yes) ; Activate Tx AGC
exten => s,n,capicommand(clamping|200) ; Activate suppression of in band DTMF tones